Harry Xu May 2012 Complex, concurrent software Precision (no false - PowerPoint PPT Presentation

Harry Xu May 2012

Complex, concurrent software Precision (no false positives) Find real bugs in real executions

Need to modify JVM (e.g., object layout, GC, or ISA-level code) Need to demonstrate realism (usually performance)

Otherwise use RoadRunner, BCEL, Pin, LLVM, …

Keeping track of stuff as the program executes?  Change application behavior (add instrumentation)  Store per-object/per-field metadata  Piggyback on GC

Keeping track of stuff as the program executes?  JVM written in Java?!  Change application behavior (add instrumentation)  Store per-object/per-field metadata  Piggyback on GC  Uninterruptible code

Jikes RVM {  Guide  Research Archive  Research mailing list

Jikes RVM {  Guide  Research Archive  Research mailing list

Jikes RVM source code Boot image writer Dynamic compilers

Jikes RVM source code Boot image Run with writer another JVM Dynamic compilers

Jikes RVM source code Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Build configurations: Base Base Jikes RVM source code Base Adaptive Full Adaptive Fast Adaptive Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Build configurations: Base Base (prototype) Jikes RVM source code Base Adaptive (prototype-opt) Full Adaptive (development) Fast Adaptive (production) Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Build configurations: Base Base Jikes RVM source code Testing Base Adaptive Full Adaptive Fast Adaptive Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Build configurations: Base Base Faster builds Jikes RVM source code Base Adaptive Full Adaptive Fast Adaptive Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Build configurations: Base Base Jikes RVM source code Base Adaptive Faster runs Full Adaptive Fast Adaptive Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Build configurations: Base Base Jikes RVM source code Base Adaptive Full Adaptive Performance Fast Adaptive Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Jikes RVM source code Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Jikes RVM source code Edit with Eclipse (see Guide) Boot image Run with writer another JVM Dynamic compilers Boot image (native code + initial heap space)

Keeping track of stuff as the program executes?  Change application behavior (add instrumentation)  Store per-object/per-field metadata  Piggyback on GC

Baseline compiler Bytecode Native code

Baseline compiler Bytecode Native code Each bytecode  several x86 instructions (BaselineCompilerImpl.java)

Baseline compiler Bytecode Native code Each bytecode  several x86 instructions (BaselineCompilerImpl.java)

Baseline compiler Bytecode Native code Profiling Adaptive optimization system

Baseline compiler Bytecode Native code Profiling (Faster) native code Optimizing compiler Adaptive optimization system

Baseline compiler Bytecode Native code Profiling (Faster) native code Optimizing compiler Adaptive optimization system

Bytecode (Faster) native code Optimizing compiler

Bytecode Resembles bytecode HIR (Faster) native code LIR Resembles typical compiler IR (3-address code) MIR Resembles assembly code

Bytecode HIR (Faster) native code LIR Opt levels: 0, 1, 2 (Even faster) native code MIR

Bytecode HIR ExpandRuntimeServices.java (Faster) Add instrumentation at native code reads, writes, allocation, LIR synchronization MIR

Keeping track of stuff as the program executes?  Change application behavior (add instrumentation)  Store per-object/per-field metadata  Piggyback on GC

header field0 field1 field2 Low address High address

Object reference type info locking & field0 field1 field2 block GC

Object reference type info locking & field0 field1 field2 block GC Object reference type info locking & Array elem0 elem1 block GC length

Object reference type info locking & field0 field1 field2 block GC Steal bits

Object reference type info locking & misc field0 field1 field2 block GC MiscHeader.java

Object reference type info locking & counter field0 field1 field2 block GC

Object reference type info locking & counter field0 field1 field2 block GC Compiles down to three Magic! x86 instructions

Object reference type info locking & counter field0 field1 field2 block GC 2 Gotcha: can’t actually use LSB of leftmost word

Object reference type info locking & counter field0 field1 field2 block GC 2 What’s the problem with this code?

Object reference type info locking & counter field0 field1 field2 block GC 2

Object reference type info locking & not used field0 field1 field2 block GC

Object reference type info locking & not used field0 field1 field2 block GC Compiles down to three x86 instructions

Object reference type info locking & misc field0 field1 field2 block GC

Object reference type info locking & misc field0 field1 field2 block GC What if GC moves object? What if GC collects object?

Keeping track of stuff as the program executes?  Change application behavior (add instrumentation)  Store per-object/per-field metadata  Piggyback on GC

Object reference type info locking & field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f)

Object reference type info locking & field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f)

Object reference type info locking & field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f)

Object reference type info locking & misc field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f) obj.misc = markAndPossiblyCopy(obj.f) worklist.push(obj.misc)

Object reference type info locking & misc field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f) obj.misc = markAndPossiblyCopy(obj.f) worklist.push(obj.misc)

Object reference type info locking & misc field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f) obj.misc = markAndPossiblyCopy(obj.f) TraceLocal.scanObject() worklist.push(obj.misc)

Object reference type info locking & field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f)

Object reference type info locking & field0 field1 field2 block GC // Initially worklist populated with roots while worklist has elements Object obj = worklist.pop() foreach reference field obj.f obj.f = markAndPossiblyCopy(obj.f) worklist.push(obj.f) TraceLocal.processNode()

Keeping track of stuff as the program executes?  Change application behavior (add instrumentation)  Store per-object/per-field metadata  Piggyback on GC  Uninterruptible code

 Normal application code can be interrupted  Allocation  GC  Synchronization & yield points  join a GC  Some VM code shouldn’t be interrupted  Heap etc. in inconsistent state  Most instrumentation can’t be interrupted  Reads & writes aren’t GC-safe points

@Uninterruptible static void myMethod(Object o) { // No allocation or synchronization // No calls to interruptible methods }

@Uninterruptible static void myMethod(Object o) { currentThread.deferGC = true; Metadata m = new Metadata(); currentThread.deferGC = false; setMiscHeader(o, offset, m); }